Vasopressin

Where it comes from

Made in

Large neurons of the supraoptic and paraventricular nuclei, whose axons end in the posterior pituitary

Sent out by

A rise in blood osmolality of one percent, a fall in blood volume or pressure, nausea, pain and stress

Acts on

• Collecting ducts of the kidney (water channels)
• Arterioles
• Pituitary corticotrophs (ACTH)
• Liver (glycogen)
• Brain circuits of social behaviour

What it does

• Puts aquaporin-2 water channels into the collecting duct so water is kept and urine concentrates
• Constricts vessels in shock, when it is released in huge amounts
• Governs pair bonding and aggression in voles, and social behaviour in people in a subtler way

In medicine

• Desmopressin, a V2-selective analogue, treats arginine vasopressin deficiency (central diabetes insipidus), bedwetting, and bleeding in haemophilia A and von Willebrand disease
• Vasopressin infusion is a second-line pressor in septic shock; terlipressin treats hepatorenal syndrome and variceal bleeding ¹
• Tolvaptan, a V2 blocker, treats low sodium from inappropriate vasopressin and slows polycystic kidney disease ²

Beyond the body’s own use

• In 778 patients with septic shock, adding vasopressin to noradrenaline did not lower mortality overall, which is why it stays a second-line rather than a first-line pressor ¹
• Tolvaptan slowed cyst growth and the loss of kidney function over three years in 1,445 patients with polycystic kidney disease, at the cost of thirst and raised liver enzymes ²
• Intranasal vasopressin improved social abilities against placebo in a pilot trial of 30 children with autism, a result that has not been repeated at scale ³
• Blocking the same system was tried too: balovaptan, a V1a blocker, improved adaptive behaviour in a phase 2 trial in men with autism, and the later trials did not confirm it ⁴